The present invention relates to a waveguide film carrier used for evaluating and mounting an RF microwave device.
In general, an RF microwave device is housed in a package. The package has internal connection terminals for a device therein. Each connection terminal extends outside the package to serve as a package input/output terminal. The film carrier of the present invention is applied between the device housed in the package and the internal connection terminals of the package.
A wire-bonding method shown in FIG. 1 is conventionally used to connect a bare-chip semiconductor as a device housed in a package to connection terminals of the package. Referring to FIG. 1, reference numeral 201 denotes a package consisting of, e.g., ceramic; 202, internal connection terminals formed in the package; 109, a bare-chip semiconductor; 110, electrode pads of the bare-chip semiconductor; and 206, wires consisting of, e.g., gold. Input/output to/from the bare-chip semiconductor is performed from each input/output terminal of the package via a corresponding wire 206. Each wire 206 is connected to a corresponding internal connection terminal by thermocompression bonding.
A second method utilizes a film-like conductor (film carrier). FIG. 2 shows a connection using a film carrier. In this method, the wires used in the method shown in FIG. 1 are replaced with a film carrier 207. As shown in FIG. 3A and 3B, a film carrier of this type is formed to have a structure comprising an insulating flexible substrate 101, an opening portion 102 formed in the insulating flexible substrate, RF electrodes 103, bias supply electrodes 104, ground electrodes 105 and the like formed on one surface (in FIGS. 3A and 3B, the lower surface) of the insulating flexible substrate, and leads 106 connected to the RF, bias supply and ground electrodes 103, 104 and 105 in the opening portion 102 formed in the insulating flexible substrate. The film carrier having this arrangement is formed as follows. That is, a conductor foil consisting of, e.g., copper is adhered on the flexible substrate 101, in which the opening portion 102 is already formed, by an adhesive 107 and formed into a predetermined shape by a general-purpose punching method. Alternatively, after a conductor foil consisting of, e.g., copper adhered on the insulating flexible substrate 101 is formed into a predetermined shape by a general-purpose punching method, the opening portion 102 is formed by using an etchant which etches only the insulating flexible substrate. In addition, a bump 108 may be formed at the distal end portion of the lead 106 by plating or the like. The bump 108 has an effect of easily and reliably forming an electrical connection between the lead 106 and the device. The bare-chip semiconductor element is connected to the film carrier as shown in FIG. 3C. That is, the electrode pad 110 formed on the surface of the bare-chip semiconductor element 109 and the distal end of the lead 106 of the film carrier are heated and connected with each other by thermocompression bonding by using a capillary 111. FIG. 3D is a perspective view in which the bare-chip semiconductor element 109 is connected to the film carrier. The film carrier connected to the semiconductor element 109 (FIG. 3D) is conveyed to a predetermined position of a mounting substrate 112 or the like. An electrode 113 formed on the mounting substrate 112 and the end of a lead 106 opposite to that connected to the bare-chip semiconductor element 109 are heated and connected with each other by thermocompression bonding by using the capillary 111. Thereafter, the resultant structure is cut at cut portions 114 shown in FIG. 3C, and unnecessary leads and insulating flexible substrate are disposed, thereby completing the device as shown in FIG. 3E. In order to house the semiconductor element in the package, the semiconductor element is connected to the internal connection terminals of the package by thermocompression bonding and unnecessary portions are disposed as described above.
In the above convention film carrier, however, since a plurality of leads are arranged to be simultaneously connected to a plurality of electrode pads formed on the surface of the bare-chip semiconductor element or the like and a plurality of internal connection terminals formed in the package, the length of each lead required for a connection must have a margin. Therefore, an inductance component corresponding to the lead length cannot be minimized. As a result, a connection between the bare-chip semiconductor element or the like and the package degrades frequency characteristics of an RF module constituted by one or a plurality of such bare-chip semiconductor elements.